The effect of Nb on recrystallization behavior of a Nb micro-alloyed steel

By the analysis of true stress-strain curves and the observation of microstructures at different deformation stages, the dynamic recrystallization (DRX) of a Nb micro-alloyed steel and a plain carbon steel is studied, and the critical stress and critical strain are determined under different deformation conditions. By the method of stress relaxation, the post-dynamic recrystallization of two steels is studied. The energy to induce recrystallization of austenite of Nb steel is higher than that of the plain carbon steel. The critical stress of DRX for Nb steel is higher than that for the carbon steel. The apparent activation energy of static recrystallization Q(srx) of Nb steel and the plain carbon steel is 318 and 231 kJ/mol, respectively. It is obvious that Nb in solid solution increases the value of apparent activation energy (Q(srx)) dramatically. The precipitation and recrystallization are in competition because of stored deformation energy. The work shows that the ratios of epsilon(p) to epsilon(c) and that of epsilon* to epsilon(c) are 1.6 and 2.2, respectively, for the steels. (C) 2007 Elsevier B.V. All rights reserved.